Strange antiparticles pop out of RHIC’s quark-gluon plasma

So far, the LHC has been spending its time ramming protons together, leaving Brookhaven's Relativistic Heavy Ion Collider (RHIC) the king of the hill when it comes to smashing larger atomic nuclei. When the nuclei of gold atoms collide within RHIC, their components dissolve into a high-energy state called a quark-gluon plasma (the LHC will eventually smash lead atoms to similar effect). A paper in today's Science describes some of the more exotic items that briefly emerge from the wreckage: the antiparticle equivalent of Deuterium, with strange quarks replacing some of the more familiar ones.

The paper itself is a mindbending trip through families of particles that are similar to our familiar protons and neutrons (termed nucleons), but have at least one of their quarks replaced by a heavier, strange version, resulting in what's termed a hyperon (four of these, Λ, Σ, Ξ, and Ω, have been observed). In the brief periods that the quark-gluon plasma exists, particles and antiparticles are equally probable, leading to a large collection of heavy and light nuclei and anti-nuclei. It also leads to some fantastic sentences, like the following: "Hypernuclei bring a third dimension into play, based on the strangeness quantum number of the nucleus, thus allowing the territory of antinuclei with nonzero strangeness."

The paper focuses on the hypertritons, atomic nuclei that consist of a proton, a neutron, and a Λ hyperon. RHIC has now produced around 200 hypertritons/antihypertritons, which survive for a couple hundred picoseconds. That's enough to determine that they are probably being formed in the same way a standard atomic nucleus is, by the condensation of their component nucleons and hyperons. In fact, they were formed in similar numbers to their less-strange equivalents, 3He and its antiparticle equivalent.

The authors take that as an indication that, at the energies produced by RHIC, strange quarks are present in equivalent numbers to their more mundane counterparts, meaning that further collisions will provide us some indication of their binding interactions, which may help shape the interior of neutron stars. So, they're gearing up to go for another round of collisions that will produce an order of magnitude more of these (literally) strange nuclei.

"...survive for a couple hundred picoseconds..." Although an infinitesimally small block of time, this phrase is nevertheless anything but precise when it says "a couple hundred picoseconds." Seems like these "mysterious" particles are actually normal particles in various stages of both decomposition and composition as a result of the collisions. Surprisingly, it doesn't appear that physicists have been able to coin a phrase for either particle creation or dissolution--apart from a conjecture about "new and mysterious" particles that last only trillionths of a second before settling down into normative particle properties.

I'm waiting for the DOI embargo to be lifted so I can see in what context such a poorly written sentence could possibly make sense.

Do they mean "Nuclei with non-zero strange quantum number are produced, so antinuclei with strange quantum number are also produced." ?

The setup on that line was the suggestion that you could more or less plot the existence of nuclei and antiparticle equivalents on a 2D grid, but that's only when you consider top/bottom quarks. Add strange quarks, and you need a 3rd dimension in order to map things.

WaltC said: "...survive for a couple hundred picoseconds..." Although an infinitesimally small block of time, this phrase is nevertheless anything but precise when it says "a couple hundred picoseconds." Seems like these "mysterious" particles are actually normal particles in various stages of both decomposition and composition as a result of the collisions. Surprisingly, it doesn't appear that physicists have been able to coin a phrase for either particle creation or dissolution--apart from a conjecture about "new and mysterious" particles that last only trillionths of a second before settling down into normative particle properties.

You have to understand that although a picosecond seems like a negligible span of time to the human brain, in the particle world it's very tangible. Time is relative and is an abstract concept our brains have formed to organize all the different forms data we process daily. From a particles' perspective, a picosecond could seem like the lifetime of a universe. Again, time is just our way of measuring the constant flux of matter, entropy and dementional space in this universe.

I would much have preferred "128.7 picoseconds," or something to that effect, but then, who's counting?...

they're counting:

Quote:

200 hypertritons/antihypertritons

and I imagine they don't reach your desired level of precision since they're averaging over 200 events.

WaltC wrote:

Seems like these "mysterious" particles are actually normal particles in various stages of both decomposition and composition as a result of the collisions.

So your saying that the particle is unstable, yes? And this is notable how?

WaltC wrote:

Surprisingly, it doesn't appear that physicists have been able to coin a phrase for either particle creation or dissolution--apart from a conjecture about "new and mysterious" particles that last only trillionths of a second before settling down into normative particle properties.

Not so new or mysterious: we've been studying hyperons for decades. And I don't understand your criticism of physicist's language skills -- I think strange is a lot better than "mysterious": what's with the scare quotes? I don't get the point of your comment other than trash talking. The idea that hypertritons are formed in similar numbers to normal matter is a big deal -- could have major significance in understanding the big bang: but since we know little about strange matter, we have to study it.

From the OP I can't tell if the hyperons decay, but it sounds like the hypertritons annihilate, so it's not like they "settle down" to "normative" particles. Regardless, a couple of 100 picoseconds is plenty of time (when it's really hot and dense) for exotic interactions.

Thanks for the article. It's interesting and a lot of us don't interact with this information on a daily basis so whether it's strange or mysterious is immaterial. Some people need to get over themselves.

"...survive for a couple hundred picoseconds..." Although an infinitesimally small block of time, this phrase is nevertheless anything but precise when it says "a couple hundred picoseconds." Seems like these "mysterious" particles are actually normal particles in various stages of both decomposition and composition as a result of the collisions. Surprisingly, it doesn't appear that physicists have been able to coin a phrase for either particle creation or dissolution--apart from a conjecture about "new and mysterious" particles that last only trillionths of a second before settling down into normative particle properties.

Wait a minute... are you confusing the particle physics meaning of the term 'strange' for the vernacular meaning?